Thermoplastic elastomers (TPE) are a class of polymers which combine the properties of two other classes of polymers, namely thermoplastics which may be reformed upon heating, and elastomers which are rubber-like polymers. One form of TPE is a block copolymer, usually containing some blocks whose polymer properties usually resemble those of thermoplastics, and some blocks whose properties usually resemble those of elastomers. Those blocks whose properties resemble thermoplastics are often referred to as "hard" blocks, while those blocks whose properties resemble elastomers are often referred to as "soft" blocks. In such TPEs, the hard blocks are believed to take the place of chemical crosslinks in traditional thermosetting elastomers, while the soft blocks provide the rubber-like properties.
The polymeric nature of the hard and soft blocks of a TPE, as well as the number of such blocks and their size (length) determines to a great extent the properties of the resulting TPE. For example, longer soft blocks usually lead to TPEs having lower initial tensile modulus, while a high percent of hard blocks leads to polymers with higher initial tensile modulus. Other properties may be affected as well. Thus manipulation on the molecular level changes the properties of TPE's, and improved TPEs are constantly being sought.
U.S. Pat. Nos. 4,331,786 and 4,230,838 describe certain poly(ether-ester-amides) which may contain polyether blocks containing tetramethylene ether repeat units. No specific mention is made of polymers containing 2-alkyltetramethylene ether repeat units.
U.S. Pat. No. 4,937,314 describes poly(ether-esters) in which a polyether soft block contains tetramethylene ether and 2-methyltetramethylene ether repeat units. No mention is made of the use of such soft blocks in poly(ether-ester-amides).
What are needed are improved thermoplastic elastomers which do not have the deficiencies of the prior art. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the detailed description of the invention which hereinafter follows.